It is known that the process for extruding thermoplastic polymers provides for an initial phase of preparation of the rubber according to the desired composition by mixing a base polymer which is filled with various additives to enhance certain features thereof in relation to others, thus bringing about various compositions of the compound suited to different uses.
The compound is subsequently extruded into the desired shapes to meet various needs.
These mixing and extrusion phases are commonly performed by individual machines, known as mixers and extruders respectively, which have certain technical features specific to the type of operation to performed. In particular it is required that the mixers be versatile and readily adaptable for mixing different compositions of the compound, and that they ensure control and regulation of the mixing temperature and high productivity.
It is also known that attempts have been made to perform the combined mixing and extrusion operation with extruders of the type provided with two parallel screw shafts acting together to achieve both feeding of the product and mixing thereof.
These machines, however, have numerous disadvantages, including low mixing capacity, particularly for certain types of compound filled with carbonates or talcs to improve the mechanical characteristics, lack of flexibility when changing the type of compound, low productivity and difficulty in controlling the temperature.